1. Field of the Invention
This invention relates to the construction of a universal paper feed cassette capable of detecting the size of recording paper housed therein, and improving the reproduction efficiency, i.e. recording efficiency.
2. Description of the Prior Art
Most of the picture recording apparati recently used, such as electrophotographic reproducing machines employ a system in which the recording paper is fed piece by piece from a cassette which houses a plurality of pieces of recording paper of a predetermined size and which is set in a predetermined position in a recording apparatus to record a picture thereon. Various cassettes according to the sizes of recording paper are provided, and they are replaced one by another every time recording paper of a different size is desired. In order to save the trouble of using different cassettes for recording paper of different sizes, a cassette capable of housing recording paper of many different sizes has been developed and put to practical use. Such a cassette is called a universal cassette and consists of a cassette body capable of housing recording paper of a maximum size, and slidable guide plates are provided in the cassette body and are adapted to stop one side edge and one end edge, i.e. a rear edge of the recording paper, the guide plates being manually moved by a user to be fixedly set. One of these guide plates, which is adapted to stop a side edge of recording paper, is called a side guide plate, and the other, which is adapted to stop an end edge, is called a rear end stopper.
Different cassettes housing therein recording paper of different sizes and used for a conventional picture recording apparatus are provided with cuts, which are formed to different shapes or in different positions in predetermined portions thereof, or with magnets attached to different positions on the rear sides thereof, so as to use different scanning distances of an optical scanning system for recording paper of different sizes. Specifically, when recording paper of a small size (for example, B5 size) is used, the optical scanning distance is shortened, and, when recording paper of a large size (for example, A3 size) is used, the optical scanning distance is lengthened. This prevents a useless operation of an optical scanning system, and allows the number of reproduced recording paper per unit time to increase greatly. Thus, the recording efficiency can be improved.
However, when a universal cassette is used in conventional recording apparatus, an optical scanning distance is determined in a fixed level irrespective of the size of the recording paper in use by the position of a magnet provided on the rear side of the cassette or the shape or position of a cut provided in a certain portion thereof. Therefore, both when recording paper of a small size is used, and, when recording paper of a large size is used, the numbers (so-called reproduction rates) of recording paper, which can be reproduced per unit time, become equal. In other words, when recording paper of a small size is used, the reproduction efficiency decreases.